Past reports have suggested that surgical trauma to the vomer during some types of cleft palate surgery may be responsible for inhibition of anteroposterior growth in the middle face. The question has been neglected; it has important clinical implications, and additional evidence is needed. In an effort to gain information about the possible influences of vomer surgery on facial growth, 24 weanling beagle dogs will be used in a 9 month longitudinal study of the effects of vomer resection. One group of 8 pups will have surgery, at the end of the 6th postnatal week, for resection of the major part of the vomer. The surgical approach will be via an access flap in the hard palate. Eight other pups will have surgery simulating that for resection, but the vomer will be left in place. A third group of 8 pups will serve as unoperated controls. Sampling will provide that each group will contain 8 unrelated pups, but that each pup will have a like-sex littermate in each of the other two groups. All pups will have tattoo marker points in the mucosa of their hard palates to enable monitoring for contraction during healing of the access flaps. Facial growth will be monitored throughout the study by x-ray cephalometry, maxillary and mandibular casts, and photography. Four additional pups will have vomer resections with subsequent sacrifice, with littermate controls, at intervals of 2, 4, 8, and 12 weeks after surgery. Tissues will be examined by light and electron microscopy in an attempt to gain information about causal mechanisms of the expected midfacial growth inhibition. The suggestion that newly identified contractile cells known as myofibroblasts might be involved in initiation of the anticipated morphogenetic aberration will be examined.